IS42S81600D, IS42S16800D
PRECHARGE
PRECHARGE Command
The PRECHARGE command (see figure) is used to deac-
tivatetheopenrowinaparticularbankortheopenrowinall
banks. The bank(s) will be available for a subsequent row
access some specified time (tRP) after the PRECHARGE
command is issued. Input A10 determines whether one or
all banks are to be precharged, and in the case where only
one bank is to be precharged, inputs BA0, BA1 select the
bank. When all banks are to be precharged, inputs BA0,
BA1 are treated as “Don’t Care.” Once a bank has been
precharged,itisintheidlestateandmustbeactivatedprior
to any READ or WRITE commands being issued to that
bank.
CLK
HIGH
CKE
CS
RAS
CAS
WE
POWER-DOWN
Power-down occurs if CKE is registered LOW coincident
with a NOP or COMMAND INHIBIT when no accesses are
in progress. If power-down occurs when all banks are idle,
thismodeisreferredtoasprechargepower-down;ifpower-
down occurs when there is a row active in either bank, this
modeisreferredtoasactivepower-down.Enteringpower-
down deactivates the input and output buffers, excluding
CKE, for maximum power savings while in standby. The
devicemaynotremaininthepower-downstatelongerthan
the refresh period (64ms) since no refresh operations are
performed in this mode.
A0-A9, A11
ALL BANKS
A10
BANK SELECT
BANK ADDRESS
BA0, BA1
The power-down state is exited by registering a NOP or
COMMAND INHIBIT and CKE HIGH at the desired clock
edge (meeting tCKS). See figure below.
POWER-DOWN
CLK
tCKS
≥ tCKS
CKE
COMMAND
NOP
NOP
ACTIVE
t
t
t
RCD
RAS
RC
All banks idle
Input buffers gated off
Enter power-down mode
Exit power-down mode
less than 64ms
DON'T CARE
Integrated Silicon Solution, Inc. — www.issi.com
47
Rev. E
07/28/08
ISSI [ INTEGRATED SILICON SOLUTION, INC ]
